High-speed networks are continually evolving. The evolution includes a continuing advancement in the operational speed of the networks. The network implementation of choice that has emerged is Ethernet networks physically connected over unshielded twisted pair wiring. Ethernet in its 10/100BASE-T form is one of the most prevalent high speed LANs (local area network) for providing connectivity between personal computers, workstations and servers.
High-speed LAN technologies include 100BASE-T (Fast Ethernet) and 1000BASE-T (Gigabit Ethernet). Fast Ethernet technology has provided a smooth evolution from 10 Megabits per second (Mbps) performance of 10BASE-T to the 100 Mbps performance of 100BASE-T. Gigabit Ethernet provides 1 Gigabit per second (Gbps) bandwidth with essentially the simplicity of Ethernet. There is a desire to increase operating performance of Ethernet to even greater data rates.
An implementation of high speed Ethernet networks includes simultaneous, full bandwidth transmission, in both directions (termed full duplex), within a selected frequency band. When configured to transmit in full duplex mode, Ethernet line cards are generally required to have transmitter and receiver sections of an Ethernet transceiver connected to each other in a parallel configuration to allow both the transmitter and receiver sections to be connected to the same twisted wiring pair for each of four pairs.
FIG. 1 shows several Ethernet twisted pair LAN connections 112, 114, 116, 118 in parallel. The first connection 112 is between a first transmitter 115a (S1A) and first receiver 125a (R1A), and a second transmitter 115b (S1B) and a second receiver 125b (R1B). The second connection 114 is between a third transmitter 135a (S2A) and third receiver 145a (R2A), and a fourth transmitter 135b (S2B) and a fourth receiver 145b (R2B). The third connection 116 is between a fifth transmitter 155a (S3A) and fifth receiver 165a (R3A), and a sixth transmitter 155b (S3B) and a sixth receiver 165b (R3B). The fourth connection 118 is between a seventh transmitter 175a (S4A) and seventh receiver 185a (R4A), and an eighth transmitter 175b (S4B) and an eighth receiver 185b (R4B). Hybrid circuits 130a, 140b, 132a, 142b, 134a, 144b, 136a, 146b are included between the transmitters and receivers.
Information such as video, audio and data, is communicated over the networks as binary values. More specifically, the information is conveyed as zeros and ones. During transmission and processing of the information, errors can be unintentionally introduced. That is, a zero may be changed to a one, or vice versa. High speed networks, such as Gigabit Ethernet are more susceptible to these errors than slower speed networks because of the increased interference.
To provide a mechanism to check for errors and in some cases to correct errors, binary data can be coded to introduce carefully designed redundancy. Coding of a unit of data produces what is commonly referred to as a codeword. Because of its redundancy, a codeword often includes more bits that the input unit of data from which the codeword was produced.
When signals arising from transmitted codewords are received or processed, the redundant information included in the codeword as observed in the signal can be used to identify and/or correct errors in transmitted data.
A class of codes referred to as low density parity check (LDPC), has emerged for use in data transmission. LDPC codes are coding schemes that use iterative decoders. It has been shown that LDPC codes can provide very good error correction for large codewords.
Longer codewords are often more reliable at error detection and correction due to the coding interaction over a larger number of bits. The use of longer codewords can be beneficial by increasing the ability to detect and correct errors. However, a difficulty in adopting LDPC code that include long codewords is the complexity of implementing the code. LDPC coding using long codewords are significantly more complex than traditionally used coding systems such as convolution codes and Reed-Solomon codes. The added complexity requires additional power.
It is desirable to have an apparatus and method for coding and decoding high speed transmission data that is complex, but yet dissipates low power.